The present invention relates to a conveyor system and the operation of a conveyor system for conveying articles, such as e.g. baggage at an airport, in which system a buffer arrangement is provided for storing and pre-sorting of at least a part of the article-flow through the system. A conveyor system for conveying and sorting articles for a number of different destinations may be operated with a much lower number of stations for discharging the articles if the possibility of pre-sorting and temporarily storing the articles exists within the system.
In particular, the invention concerns a storage rack for storing articles and a conveyor system comprising such a storage rack.
A sorting and storage system for pieces of goods such as flight luggage is disclosed in U.S. Pat. No. 5,301,790, in which the luggage is placed on totes situated on a conveyor with tiltable carrying platforms. The luggage may be conveyed directly to one of a number of destinations where it is unloaded from the tote, or it may be temporarily placed in a storage unit until a destination for that particular luggage is opened, whereupon the luggage is conveyed to that destination and unloaded from the tote.
Storage systems for storing early bags in a baggage handling system are also disclosed in U.S. Pat. No. 5,413,205 and U.S. Pat. No. 5,575,375. These storage systems comprise a conveyor with multiple tray carriers arranged in a serpentine fashion for efficient use of horizontal space. Such storage systems are primarily used for storage of so-called early bags for which the destinations are not opened yet.
Conveyor systems for e.g. airports for conveying and sorting items, such as luggage, for a number of different destinations need to have a high number of discharge stations for discharging items for specific destinations, because a number of the items that pass the system are entered into the system several hours before the term for discharging the items, e.g. at the make-up operation for a desired flight departure. Therefore, a discharge station must be open for items for a specific destination for a long period of time before the term for discharge for that specific destination, thus requiring the system to comprise a high number of discharge stations. Furthermore, some items arrive to the conveyor system much earlier than the aforementioned items, often referred to in terms of airport systems as xe2x80x9cearly bagsxe2x80x9d, which is baggage that is checked-in very early or baggage in transit. Most systems include an early bag storage unit, such as one or more long conveyors upon which the early bags may be temporarily stored until a discharge station is opened for baggage with the specific destination of the early bags.
A high number of discharge stations are costly to install and to maintain and they take up very large areas because of the area requirements for providing access for trucks etc. to each discharge station. Also, the early bag storage units that are formed as long endless conveyors take up plenty of area, for which reason the capacity of those storage units have to be limited.
It is thus an object of the present invention to provide a conveyor system with means for reducing the number of discharge stations required for an efficient operation of the system without reducing the sorting capacity or the conveying capacity of the system.
It is a further object of the invention to provide a storage arrangement that enables pre-sorting of the stored items according to their destination and/or the their term of departure so that items with a specific destination may be retracted quickly from the storage arrangement and moved to a discharge station dedicated to that specific destination.
It is a still further object to provide a storage arrangement in which the items may be stored in a compact manner so that the area requirements for the storage arrangement are low.
It is an advantage that the items are placed on trays before they are entered onto the conveyor in order to minimise the risk of damaging the items when they are conveyed and to prevent that parts of the items, such as e.g. handles or belts, get stuck in the conveyor parts. Furthermore, the trays are more easy to convey and handle by the conveyor systems and especially for a storage arrangement since they are uniform objects in contrast to e.g. baggage.
Thus the present invention relates to a method of conveying items using a system comprising conveyors and at least one article storage arrangement,
(a) loading items onto trays at at least one loading station of a first conveyor,
each item being identified and assigned to a destination belonging to a group of predefined destinations,
xe2x80x83to thereby create articles, each article consisting of a tray carrying at least one item,
(b) conveying articles in the first conveyor, the first conveyor being capable of conveying articles from the at least one loading station to an article storage arrangement comprising a plurality of storage units in each of which a plurality of articles may be stored,
(c) moving at least some of the articles from the first conveyor into storage units of the articles storage arrangement,
(d) determining to which set of articles belonging to a predefined group of sets each of said articles belongs according to the destination of the at least one item of the article, at least one of the plurality of storage units being assigned to each of said sets,
(e) storing each article in one of the at least one storage unit being assigned to the set to which the article belongs,
(f) allocating at least one discharge station of a second conveyor,
the second conveyor being adapted to convey articles from the article storage arrangement to the at least one discharge station,
xe2x80x83to a destination belonging to the group of predefined destinations,
(g) moving at least some of the articles stored in the article storage arrangement and
being assigned to said destination from the storage units and to the second conveyor,
(h) conveying said articles in the second conveyor to said discharge station, and
(i) discharging the items from the trays of said articles at said discharge station.
A plurality of storage units within the storage arrangement makes it possible to pre-sort the articles when they enters the article storage arrangement. The control means for controlling the operation of the conveyor system may comprise a central control unit that controls all operations or it may comprise a number of distributed units that each controls a part of the conveyor system, and preferably control means comprise a combination of a central control unit and a number of distributed units. The control means may further comprise a number of sensor means, such as photo cells or photosensors, cameras, stress sensitive sensors etc., for detecting the presence of articles at various positions on the conveyor system, sensor means for detecting the conveying speed at various positions along the conveyor system, data entering means for manually entering data into the control system, scanning means for scanning identification marks of items and/or trays conveyed by the system, etc.
It is an advantage for efficient operation of the system that substantially all of the articles are entered into the article storage arrangement in step (c) so that the discharge stations only have to be allocated to receive items for a given destination for a short period at a time, typically a period of the order of 5-15 minutes, because the articles to be conveyed to the discharge station within the period are present in the article storage arrangement. Thus, the discharge station is only occupied for the short period in which at least a part of the amount of items for a given destination are discharged, and the discharge station may be allocated to another destination. The discharge stations are utilised very intensively by this method and the number of discharge stations for a conveyor system of a given sorting capacity maybe reduced with 30-80%, depending on the composition of the article flow through the system.
According to a preferred embodiment of the present invention, at least some of the predefined sets of articles solely comprise articles of which the items are assigned to the same destination.
Substantially each of the destinations has a scheduled departure time associated with it and an additional or alternative way of defining the sets is that at least some of the predefined sets of articles solely comprise articles of which the items are assigned to destinations having a scheduled departure time within a predefined time range. In particular, said sets may be defined so that the predefined time range of any of said sets does not overlap the predefined time range of any of the other of said sets.
The two above described ways of defining sets may be combined so that articles assigned to destinations having late departure times are pre-sorted to time-range defined sets which are emptied and pre-sorted to sets defined for given destinations at the time where the latter sets are defined so that the method according to the invention further comprises the steps of
(j) assigning at least one of the plurality of storage units to a predefined set of articles solely comprising articles of which the items are assigned to a given destination,
(k) moving articles of which the items are assigned to said destination from the at least one storage unit assigned to the set of articles of which the predefined time range includes the departure time of said destination to the at least one storage unit having been assigned in step (j).
It is an advantage for the efficiency of the utilisation of the discharge stations if step (f) is a temporary allocation to a destination during which a subset of a total expected number of items being assigned to said destination is discharged at said discharge station, the subset being selected from the items stored in the article storage means. Consequently, an operation of discharging the total number of items for a given destination comprises a plurality of temporary allocations of one or more of the at least one discharge stations.
In order to keep track of which items are present in a given container means for containing items, e.g. for security reasons at airports etc., the whole subset of items may subsequent to the discharging be stored in one container means for containing items. Furthermore, a control means associated with the system may be arranged to produce an output comprising data that are significant for the identity of each of the items within the subset of items.
Substantially each of the storage units of the storage arrangement is in a preferred embodiment of the invention designed for permitting a plurality of articles to be disposed aligned in abutting proximity to each other longitudinally along a generally horizontally elongated storage bay, each storage unit comprising a frame defining said storage bay and support means for supporting the articles to be stored in the storage unit. By designing the storage units in this manner, it is achieved that the articles may be stored very densely, thus taking up a minimal area of space. This is in particular possible because the items to be conveyed by the conveyor system are placed in trays.
The support means may e.g. consist of pairs of tracks on which the articles are resting or the support means may preferably comprise cylindrical rollers or wheels so that the articles may slide into and out from the storage bay with a minimum of friction. The support means may comprise conveyor belts or driven cylinders or wheels so that the articles may be moved within the storage bay, e.g. when they are to be retracted from the storage bay.
The support means of each of the storage units may be arranged slightly downwardly inclined towards a front end in the longitudinal direction of the storage bay of said storage unit so that articles stored in the storage unit will be drawn towards said front end by the force of gravity acting on the articles, each of the storage units further comprises
movable stopping means that may be positioned so that the stopping means of said storage unit prevent articles stored in said storage unit from passing the front end of the storage bay of said storage unit, and
means for moving the stopping means of said storage unit between a position where the stopping means prevent articles stored in said storage unit from passing the front end of the storage bay of said storage unit and a position where the stopping means allow articles to pass said front end.
In which case the storing of an article in a storage unit according to step (e) comprises the steps of
(e1) moving the article to the front end of the storage unit,
(e2) in case a previous article already resides in the storage unit, placing the article in abutting contact with the previous article so as to prevent the previous article from passing the front end of the storage unit when the stopping means are moved to the position where the stopping means allows articles to pass said front end,
(e3) moving the stopping means of the storage unit to the position where the stopping means allow articles to pass said front end,
(e4) moving the article into the storage unit by means of pushing means whereby the previous article is moved further into the storage unit, and
(e5) moving the stopping means of the storage unit to the position where the stopping means prevent articles from passing said front end,
and wherein the removal of an article from a storage unit according to step (g) comprises the steps of
(g1) engaging the article being in a front end position at the storage unit with withdrawing means so as to prevent the article from passing the front end of the storage unit when the stopping means are moved to the position where the stopping means allow articles to pass said front end,
(g2) moving the stopping means of the storage unit to the position where the stopping means allow articles to pass said front end,
(g3) moving the article from the storage unit by means of the withdrawing means whereby one or more possible further articles present in the storage unit are moved further towards the front end of the storage unit, any article being in abutting contact with the article that is moved from the storage unit being moved to the front end position of the storage unit, and
(g4) moving the stopping means of the storage unit to the position where the stopping means prevent articles from passing said front end.
Articles may with this particular arrangement be loaded into and retracted from the storage unit from the front end and the storage bays do not have to be equipped with any active means for driving the articles or controlling the position of the articles stored within the storage bay.
In order to enable storage of articles in a dense manner, a plurality of storage units may be arranged in a storage rack in at least two vertically spaced generally horizontal levels, said storage units being arranged so that the longitudinal direction of the storage bays of said plurality of storage units are substantially parallel and so that the front ends of the storage bays of said plurality of storage units are arranged in substantially the same vertical plane. By arranging the front ends of the storage bays in substantially the same vertical plane, it is enabled that articles may be loaded into and retracted from the plurality of storage units by an article handling system that is at least partly shared by the storage units
In particular, such storage rack may comprise
elevating means for moving articles between the at least two horizontal levels;
shifting means for moving articles in a horizontal level, the shifting means being arranged in a vertical plans substantially parallel to the vertical plane of the front ends of the storage bays of said plurality of storage units,
first transferring means for transferring articles between the elevating means and the shifting means,
second transferring means for transferring articles between the elevating means and the first and the second conveyor,
loading means comprising pushing means for loading articles from the shifting means into the storage units, and
unloading means comprising withdrawing means for unloading articles from the storage units onto the shifting means,
so that step (e) of moving articles from the first conveyor and to each of the plurality of storage means arranged in the storage rack and step (g) of moving articles from each of the plurality of storage units arranged in the storage rack and to the second conveyor may be performed by means of the elevating means, the shifting means, the first transferring means, the second transferring means, the loading means and the unloading means of said storage rack.
The elevating means may in a preferred embodiment comprise two lifts, one lift arranged at one side of the storage rack for loading articles into the rack and one lift arranged at the opposite side of the first lift for retracting articles from the rack. The elevating means are preferably arranged in substantially the same vertical plane as the shifting means so that articles may easily be transferred between the elevating means and the shifting means.
The system may be operated by means of a central control unit that is enabled to control each step from check-in of an article and until the article is discharged from the conveying system, including the position of each article within the system, or the or the control means may comprise a number of distributed control units, or the control means may preferably comprise a combination of distributed control units and one or more central control units. It is, regardless of the type of control means applied, an advantage for a method according to the present invention that each article is labelled with a unique, automatically readable identification mark and the system comprises reading means for reading the identification marks and producing an output accordingly, the reading means being situated at least at one position along the path of the articles, the method further comprising the steps of
reading the identification marks of substantially each article passing each of the at least one reading means,
producing an output from the reading means according to each of the identification mark read, and
communicating said output to the control means of the system.
An identification mark may be placed on the tray, in which case the control means should comprise a central control unit comprising means for storing and retrieving data concerning the identity of each of the items being conveyed by the system and data concerning the identity of the tray on which each of said items is placed on. The coupling between the identity data of the item and the identity data of the tray on which the item is placed is advantageously established at the loading station.
The identity of an item comprises the destination of the item, which comprises the identity of the flight departure in case of an baggage handling system for an airport. Further, the identity may comprise data identifying the owner of the item. The identification mark may be any kind of mark comprising information or data, that are automatically readable, such as e.g. a bar code, a radio transponder that emits a radio signal comprising an identification code upon receiving a request signal, visual codes that may be read by one or more optical sensors, a character code, that is both automatically readable with an optical character recognition system and readable by human operators, mechanical codes in the form of holes or indentations, a pattern of magnetic plates, such as steel plates, that is detectable with inductive sensors, etc.
The advantages of placing an identification mark on the tray are that it enables a nearly completely faultless reading of the identification marks, since the trays are largely uniform, at least in one of its dimensions, and the mark should have substantially the same position on all trays so that the marks can be read by automatic reading means. These reading means may be used for control purposes e.g. to ensure that the articles actually are discharged from the conveyor system at the correct discharge station, for restarting purposes in situations where parts of the system have been out of operation for a period, especially for systems with distributed control, in which identification data in the distributed control units may have been lost, for identification purposes to identify an article prior to a handling operation such as X-ray scanning, separation, loading or discharge of an item, etc.
The first and the second conveyor may meet in a separation unit arranged so that articles are transferred to the separation unit from the first conveyor and articles may be transferred from the separation unit to the second conveyor or to the article storage arrangement, the separation unit comprising means for transferring a given article from the separation unit to either the second conveyor or the article storage arrangement depending on the identity of the article, said means being controlled by the control means for controlling the operation of the conveyor system.
The method of the present invention is preferably used for operation of a conveyor system in which the control means of the system comprises a number of distributed control units. According to such an embodiment, the first and the second conveyors each comprises a plurality of conveyor sections arranged in series, each given conveyor section comprising a control unit and data communication means, data relating to the identity of an article that is passing from the preceding conveyor section to the given conveyor section being communicated from the control unit of the preceding conveyor section to the control unit of the given conveyor section by the data communication section of the preceding conveyor section.
Furthermore, the control means of the system for controlling the operation of the system and perform the method of the present invention by means of the system may comprise a central control unit that has data stored regarding the identity of the items placed on each tray, so that it from the identification of the tray and these data is possible to determine whether a given tray should be conveyed to one of the discharge station or should be conveyed to the storage arrangement. Thus, the separation unit may comprise a control unit and data communication means, the data communication means be adapted to communicate data relating to the identity of an article that is passing from the preceding conveyor section to the separation unit from the control unit of the preceding conveyor section to the control unit of the separation unit, the data communication means further being adapted to communicate data relating to the identity of an article that is passing from the separation unit from the control unit of the separation unit and to either the control unit of the adjacent conveyor section of the second conveyor or to a control unit controlling the article storage arrangement, the control unit of the separation unit being adapted to control the means for transferring a given article from the separation unit to either the second conveyor or the article storage arrangement. Additionally, the separation unit may comprise data communication means for communication data regarding whether a given article is to be transferred to the article storage arrangement or to the second conveyor from the central control unit and to the control unit of the separation unit. The communication between the separation unit and the central control unit could be arranged so that the central unit by communication means keeps a updated table in the control unit of the separation unit regarding which articles should be conveyed to the discharge stations and which articles should be conveyed to the storage arrangement, or the control unit of the separation unit could make a request to the central control unit regarding the direction of each article that arrives at the separation unit.
The system may furthermore comprise an X-ray unit for X-ray screening the items conveyed by the system and a diversion unit for receiving rejected articles, said X-ray unit being arranged so that articles pass the X-ray unit when being conveyed by the first conveyor, the X-ray unit comprises means for diverting articles to the diversion unit depending on the result of the screening, the operation of said means and of the X-ray unit being controlled by the control means for controlling the operation of the conveyor system.
It is also advantageous for the efficiency and flexibility of the present method that each of the discharge stations comprises a control unit for controlling the discharge of articles from the conveyor and data communication means being adapted to communicate data relating to the identity of an article passing from the previous conveyor section to the discharge station from the control unit of the previous conveyor section and to the control unit of the discharge station, the data communicating means further being adapted to communicate data relating to the identity of an article passing from the discharge station to a following conveyor section from the control unit of the discharge station and to the control unit of the following conveyor section.
The trays that are used with the system are advantageously shaped so that they have an upper surface of a concave shape as viewed in a cross-section perpendicular to the longitudinal direction of the conveyors so as to avoid that items carried by the trays may fall off during transportation. Furthermore, the upper surface of the trays is preferably coated with a friction increasing material so as to prevent items carried by the trays from falling off during transportation. A suitable shape as well as surface coating of the trays increase the acceleration that may be applied to the trays in a direction transversal to the conveying direction in order to discharge the trays from the conveyor without causing the items carried on the trays to fall off during the discharging operation, thus enabling a more efficient discharge of trays from the conveyor.
Furthermore, the system may comprise a return conveyor for returning empty trays from the at least one discharging station to the at least one loading station.
The present invention relates also to the conveyor system described above by means of which the method of the present invention is carried out as well as to the storage rack as described.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed.